Police in Perth have charged a 26-year-old man over a slave labour racket.

It's alleged the man, an Estonian national, operated a labour hire company that specialised in finding work for foreign nationals.

But police allege once he lured workers to Perth by assisting with visas, airfares and accommodation, he confiscated their passports and took control of their bank accounts.

Demands for money were made by the accused and the victims told they would be found work, with their wages going into the arranged bank accounts, from which they would be given a small allowance to live off while the rest of the funds were kept by the accused.

Detective Sergeant Ken Foster says the victims took a number of months to tell police about the alleged racket .

"The difficulties are that they come from different parts of the world where their views of policing are somewhat different to what we understand them here," he said.

"They are frightened of that type of thing and they are also a long way from home.

"Threats were made against them and not only them but also their families in Estonia and all they wanted to do was get out of the place."

The 26-year-old man has been charged with human trafficking and debt bondage.

Police say another three men, all Estonian nationals, who entered Australia on student visas, were charged with extortion and unlawful possession of foreign passports late last year.

All four men are due to appear in court in Perth in April.

The arrests were a result of a joint operation between WA Police, Australian Federal Police and the Department of Immigration and Citizenship.

A department spokesman said people should check online businesses offering work or visas in Australia.

"If someone is offering online assistance with an Australian visa and there is nothing showing they are either a registered migration agent or a DIAC endorsed website, keep looking," he said.